package org.andengine.engine;

import org.andengine.engine.options.EngineOptions;
import org.andengine.util.time.TimeConstants;

/**
 * A subclass of {@link Engine} that tries to achieve a specific amount of
 * updates per second. When the time since the last update is bigger long the
 * steplength, additional updates are executed.
 * <p/>
 * (c) 2010 Nicolas Gramlich
 * (c) 2011 Zynga Inc.
 *
 * @author Nicolas Gramlich
 * @since 10:17:47 - 02.08.2010
 */
public class LimitedFPSEngine extends Engine {
    // ===========================================================
    // Constants
    // ===========================================================

    // ===========================================================
    // Fields
    // ===========================================================

    private final long mPreferredFrameLengthNanoseconds;

    // ===========================================================
    // Constructors
    // ===========================================================

    public LimitedFPSEngine(final EngineOptions pEngineOptions, final int pFramesPerSecond) {
        super(pEngineOptions);
        this.mPreferredFrameLengthNanoseconds = TimeConstants.NANOSECONDS_PER_SECOND / pFramesPerSecond;
    }

    // ===========================================================
    // Getter & Setter
    // ===========================================================

    // ===========================================================
    // Methods for/from SuperClass/Interfaces
    // ===========================================================

    @Override
    public void onUpdate(final long pNanosecondsElapsed) throws InterruptedException {
        final long preferredFrameLengthNanoseconds = this.mPreferredFrameLengthNanoseconds;
        final long deltaFrameLengthNanoseconds = preferredFrameLengthNanoseconds - pNanosecondsElapsed;

        if (deltaFrameLengthNanoseconds <= 0) {
            super.onUpdate(pNanosecondsElapsed);
        } else {
            final int sleepTimeMilliseconds = (int) (deltaFrameLengthNanoseconds / TimeConstants.NANOSECONDS_PER_MILLISECOND);

            Thread.sleep(sleepTimeMilliseconds);
            super.onUpdate(pNanosecondsElapsed + deltaFrameLengthNanoseconds);
        }
    }

    // ===========================================================
    // Methods
    // ===========================================================

    // ===========================================================
    // Inner and Anonymous Classes
    // ===========================================================
}
